Mechanical Harvesting of Southern Highbush Blueberries

and Postharvest Disease Relationships

Part of comprehensive 4-year research/ extension project to take southern highbush production to next level

Main themes:1) Overcome genetic, horticultural, and engineering barriers that

stand in the way of mechanical harvesting for fresh market

2) Improve overall fruit quality and microbial safety

3) Address emerging systemic diseases that threaten the industry

Bill Cline

Mainland, C. M. et. al. (1975) The Effect of Mechanical Harvesting on Yield, Quality of Fruit and Bush Damage on Highbush Blueberry. J.A.S.H.S. 100:129-134

Machine harvesting reduced yields of marketable fruit by 19 to 44%

10 to 30% softer than hand harvested fruit Machine harvested fruit developed 11 to 41%

more decay after 7 days storage at 70oF Sorting increased rots of mechanically harvested

fruit by an additional 5 to 10%

Slide courtesy Bill Cline, NCSU

Can we do better than this, utilizing the novel, crispy-flesh SHB cultivars?

Potential disease/ pathogen issues associated with machine-harvest

• Bush damage, especially at base of plant, due to harvester’s catch pans– Entry points for stem blight and canker

pathogens

• Fruit bruising due to direct contact with harvester’s beater rods or as result of fruit falling in harvester– Internal cell damage and leakage– Increased susceptibility to postharvest

decay– Potential attachment sites for microbial

contaminants of food safety concern

Minimizing crown injuryassociated diseases

• Proper pruning, cultivar selection (narrow crown), grafting• Careful harvester operation• More gentle catch pan designs (e.g. “centipede scales”)

BEI International

Where and how does fruit bruising occur during harvest and postharvest process?

BIRD (Blueberry Impact Recording Device)

Changying Li Pengcheng Yu

BIRD sensor node

PC-BIRD software: data acquisition

PC-BIRD software: data analysis

Downloading/recharging interface

C. Li

BIRD (Blueberry Impact Recording Device)

BIRD (Blueberry Impact Recording Device) during mechanical harvest with Korvan 8000

Time (second)

0 2 4 6 8 10

Acc

ele

ratio

n (G

)

0

100

200

300

400

Blueberry interaction with rotary head and falling on the fisher scale

Transportation on conveyer belt

Falling on lug

Bruising, machine harvest and postharvest decay

Crispy berries as a potential game-changing technology

Conventional SHB cultivars such as Star, Emerald, Scintilla, Primadonna Lower firmness than rabbiteyes

Novel crisp-textured SHB cultivars Focus of UF, NCSU, and UGA breeding

programs Firmer berries, more “spingy” than

conventional cultivars e.g. Sweetcrisp, Indigoblue, Suzieblue

Machine-harvesting of crispy SHB cultivars may be feasible with reduced bruising and postharvest decay

Lucky Mehra

Compare conventional and crisp-textured SHB genotypes after hand- or mechanical-harvest in relation to:1. microbial contamination on fruit at harvest 2. subsequent postharvest decay development

Identify fungal organisms associated with postharvest decay

Bruising, machine harvest and postharvest decay

Cultivars and harvesting (Waldo, FL)

4 replicate row sections

Conventional type Star, Scintilla (2009/2010) FL 01-248, Primadonna (2009)

OR

Cold storage for 0, 7, 14, and 21 days, room temp for 4 days

Crispy/ semi-crisp type Sweetcrisp, Farthing

(2009/2010) FL 98-325 (2009)

Natural disease development in cold storage

Average of 3 cultivars per flesh type

Source 2009 2010ndf ddf F P ndf ddf F P

Flesh type (F)Harvest (H)F × HTime (T)b

T × FT × HT × F × H

1113333

666

164164164164

62.75139.53

2.5553.301.534.08

0.610

0.0002<0.0001

0.162<0.0001

0.2090.0080.609

1112222

666

120120120120

274.5157.818.410.42.83

0.2700.030

<0.0001<0.0001

0.005<0.0001

0.0630.7610.967

Disease incidence in relation to firmness

Data from all 6 cultivars over 4 assessment dates

Inverse relationshipIn 2009, >220 g/mm associated with low diseaseIn 2010, firmness reached desired levels only in few cases

Contribution by different fungal genera

Data from all 4 cultivars over 4 assessment dates

Alternaria spp., Cladosporium spp., and Aureobasidium pullulans most common

Complex of fungi similar across treatments

Higher proportion of Colletotrichum in 2010

Cladosporium spp. and Aureobasidium pullulans

Cladosporium infection limited to velvety mycelial tuft visible at stem scar or cracks near scar

A. pullulans: wet and slimy appearance of berries

MSUImages courtesy Wharton & Schilder

Cladosporium Aureobasidium

Alternaria, Botrytis and Colletotrichum spp.

MSU

Alternaria spp. Botrytis spp.

Colletotrichum spp.Images courtesy Wharton & SchilderImages courtesy Wharton & Schilder

$23 at AgScience, Inc.Auburndale, FLagsciencebookstore.com

Microbial fruit surface contaminants

Overall contaminant counts (aerobic bacteria, yeast, mold) below commonly used thresholds for processed blueberries

No effect of harvest method or flesh typeNo E. coli detected in either yearColiforms detected in:

o One rep of hand-harvested Primadonna in 2009 (avg. 7 CFU/g)

o Machine-harvested reps of Farthing and Sweetcrisp in 2010 (avg. 1 and 20 CFU/g, respectively)

ConclusionsNo significant effect of flesh type and harvest method on

microbial contaminantsNatural decay incidence: Lower for hand-harvested fruit; for

crispy flesh typeMachine-harvested crispy flesh equal to or lower than

hand-harvested conventional fleshFruit firmness good predictor of post-harvest decay;

>220 g/mm desirableCladosporium, Alternaria, and Aureobasidium most

commonArtificial inoculation: Lower decay incidence for crispy flesh

Machine-harvested crispy SHB acceptable in terms of postharvest disease and quality

Overall Bottom Line from Mechanical Harvesting Experiments

• For most quality and postharvest attributes, hand-harvested conventional and machine-harvested crispy equivalent

• Stay on top of optimal harvest window, avoid hot temperatures

• Field losses (ground drops) still problematic, but can be addressed with pruning, cultural practices, and breeding

• Economics: cautiously optimistic

Fresh-pack blueberry practices to reduce postharvest decay

Select cultivars for resistance, dry stem scar, crispy fruit

Use preharvest fungicides Timely, thorough harvest (every 4-7 days for

highbush, 7-10 day for rabbiteye) Handle berries dry Provide a clean pick/pack environment Cool (dry) pre-pack followed by forced air

Slide courtesy Bill Cline, NCSU